CVE Chelmer Valve 738-196 | electronic tube BRIEF DESCRIPTION: This valve is a beam tetrode with metal-shell wafer, octal base designed for use : Specifically in the output stage of an audio frequency amplifier. KT88 continuous output of up to 100 watts. At reduced power, used in ultra linear mode, push-pull, maximum distortion can be limited to 2% at 70 watts or 1% at 30 watts output. Two valves in class AB1 can give a are in line. directly above another. HEATER CHARACTERISTICS Vby ceeeeeesesseseseneeescessssererensnseeneneaeestsnsesiceceees 6.3.V Tetrode Connected [py ceceeeeeeceuesceecteeccceseseeseeesessecseeeeeesssetsarsarsceeces 16 A Vig ccteeceececeeeeeceeecssccseeesensecanecs 250 Vv MAXIMUM RATINGS Vo? beeen ee ee uence enneaeseesessseesueeentes 250 Vv Absolute Design Maximum Lc eteeeeeseceseceuseseasesceeseneeevseanees 140 mA Vig ieteseeessccceecenereeeaes 800 800 Vv 192 (APPFOX) oo... ee ceeeceeeeeeeeueeees 3 mA Vs2 cee daecaseaeeseeeeeeates 600 600 Vv -Ve1 (APPTOX) ...... eee ceeeeeeeeeee 15 Vv Vag? ctsteceseseeeseeneees 600 600 Vv Bin cteceeceseseeeeeeeeestasseseesieseaeeass 11.5 mA/V Vel we eeeeoeeaseneeseesneues 200 200 v Vg cect ec eet eeeeeeececeentageresenessscesenes 12 kQ Pag ccscsesceescestereeeatenes 42 35 Ww Wal g2 cerecesesesesssesesesecseeeeeeseeee 8 Pp? te eeeceseveeeceeeeaeeranes 8 6 Ww Pang? ctereeesserseeeeeeeeees 46 40 Ww Triode Connected Vy ceseecneceueeneesseeece scene 230 230 mA VAeK cceceeeeeeeeeeseerereees 250 200 Vv Vag? sib e eens eee cere eceeecscessenesaseees 250 v Thully cccceeesceceeneeeceeees 250 250 c Tasg2 Sees et see eeeeeeeceeesbeseueescuesecees 143 mA Rei-k (cathode Bias) Voi C15) 1 <0) 9 rr 15 Vv Pa+g2=35W bene ee see een ee ee eens eataeenees 470 kQ Br cece c eee ee ees ee nee ee esta cereeeaeccscaes 12 mA/V Parg2735W cence ee eee eeeeeeteeceececeeeeaes 270 kQ Dy crite eee eece eee eeeeseeteecseeeeeetteeetenees 670 Q Rei-k (fixed bias) Ho cece cesceeeeeteceeceeeeseectsscustecseasenes 8 Paeg2=35W se ese beeen ee ee tee saeseenecenes 220 kQ Parg2? 35 W ce eet eee eeedeebeneeeeeseeneneees 100 kQ TYPICAL OPERATION CAPACITANCES (Measured on a cold unscreened valve) Push-Pull. Class AB1. Cathode Bias. Tetrode Connection. Triode Connection Tetrode Connection Va(b) vee e states nsec en eneeseeessceeneeee 560 Vv Va(o) seen cnet eeeceecsceaecensesecacaesas 21 Vv Cy1-ag2 be beeeeeeeeeene 7.9pF Cola bebe eeeececeuteeeeeaes 1.2 pF Ve? cheese ee eeeeeeeeeeeceseseeseeatanees 300 Vv Cyt -all less ag? --- 9.3pF Cyr all less q creer 16 pF lao) Ween ee nee eee e te eeeeeeneeceeeeens 2x64 mA Cag? all less gl -- 17 pF Ca all less gl oe 12 pF In (max Sig) vrrttseessseeeseeeeeeee 2x73 mA 152(0) Uae tbe e ees eaeeeeeesesevecenvegunes 2x1.7 mA OUTLINE g2 (max sig) teeters: 2x9 mA Ri(a-a) bebe e eee ee ee ne eeseeeeseeenenes 9 kQ AR ceceseeseeceseesesesesesecsereaes 2x460 Q . ~Ve1 (APProx) ... 0... ceeeeeeeaee 30 Vv ee 50 WwW Dot cceeeteseeeetseeeeestteeseesceeee 3 % ase: Mota anell water octal FIM ccc reteeeseaeeses i % 110 2 dia : Pao) been e eens eee en neaecenecneseeesene 2x33 WwW 125 Pin: 1 base shell gt Pa (Max Sig) ceceeeteeeereereee 2x12 WwW oh 6 NP Pp2(0) weet eee eeceesecececeneateeneeans 2x0.5 W 3 a th Po? (max sig) ccrrtetete eters 2x2.7 W 4 g2 8 kbp V(gi-g1 (ac) CIESt 22... cece eee eeee 60 Vv { AT See notes, Page 2. : Dimensions mm and are maximum INSTALLATION: The tube may be mounted either vertically or horizontally. When tubes are mounted vertically it is recommended that the centres of the tube sockets are not less than 4 inches apart and that pins 4 and 8 of each tube When tubes are mounted horizontally it is recommended that the centres of the tube sockets are not less than 4 inches apart and that pins 4 and 8 of each tube are in the same vertical line. Free air circulation around the tube is desirable. One tube should not be mounted:Chelmer Valve KT88 electronic tube Push-Pull. Class ABt. Tetrode Connection. Fixed Bias. Push-Pull. Class AB1. Fixed Bias. (40% Tapping Points) Ultra-Linear Connection. (40% Tapping Points) Ultra-Linear Connection OUT torrie eter ee ees e res eeneaes Pa+g2(o) ween eeesecesenusceees arg? (max sig) Seba sevanene V(gi-g1 Yfac) CFeSt we. Tt 500 375 v 436 328 Vv 2x87 2x87 mA 2x99 2x96 mA . 6 5 kQ 2x600 2x400 Q $2 35 v 50 30 WwW 1.5 I % 4 3 % 2x38 2x28.5 W 2x17 2x16 WwW 104 71 Vv 4.8 4.5 kQ Triode Connection la+g2(0) TEC e atte ware ecear Ri(a-a) bebe eeeeeeeaenesas Pa+g2(o) Vet eee eeeeeeen ee Pasg2 (max sig) +--+" Ry eececeneceseceeseeeees V(g1-g1)(ac) crest ..., DUE crete tet eeeeceeee anaes Vab) sateen eeeeereeeeensunacecerectes 560 Vv Vag2(b) tea easceeneseessnncveepecvas 560 460 Vv Va(o) weet ee nee eer ceeeeseseseeveesaetees 552 Vv ABI(O) creeresseeeteeteeee testers 553 453 Vv Ve? cee e ates sec eceeeeseneaeseeccneceasaes 300 Vv Atg2(O) ceecceseeeteeeseeeeeeeetees 2x50 2x50 mA lao) poet eeeeeeeeeceeeseusaceeavaeenaeans 2x60 mA lag? (max sig) sereeee eee 2x157 2x140 mA In (max Sig) ccrrcteeteeeeeeeeseeeees 2x145 mA Ri (a-a) see eeaneeseneeseesevecesenes 4.5 4 kQ 152(0) Wie ee ee eeee ent eeeteeeeeeeeeeenenes 2x1.7 mA *-Vor (approx) oo... 75 59 Vv g2 (max Sig) rete eee 2x15 mA OUL tctecr tree eeseeseeeeceneeeceeees 100 70 WwW Ri (a-a) fae eee eee eeeecaeeeeeeeaeeeees 4.5 kQ Dit ceccceceeeeeeeeceesseeueeseececs 2 2 % "Voi (Approx) ...... 34 Vv FEM oicccecccccceeeeccccceceteee. It 10 % OUL ett eeece eer eceeeceecceeteeseneees 100 WwW Pa+g2(0) seen ea eceeceneeeteaseaeens 2x27.5 2x22.5 WwW Diot tenes neeeceteecesscesscuseecsensenns 2.5 % Pasg2 (max sig) scrtttreeee 2x33 2x27 WwW FEM eeccecetcseseteleneeseesees 10% Vigi-gi)(ac) CFESt ..e.eseeeee 140 114 Vv Pa(o) sa eeeeecsceencnceesaveesececcenens 2x33 WwW OUL crc et eet een eeteseeescnseeneenes 7 6.5 kQ a (max sig) ccrrceeesreeeeeeteeeees 2x28 WwW P52(0) vee b ee eeeeaceneesetectscesennecs 2x4.5 W Poa (max sig) sneer eeceeceeeneee 2x4.5 WwW V(gi-gi)(ac) Crest ...........c. ce, 67 Vv Push-Pull. Class AB1. Cathode Bias. Push-pull. Class ABl. Cathode Bias 400 485 Vv 349 422 Vv 2x79 2x94 mA 2x80 2x101 mA 4 4 kQ 40 50 V "47 31 Ww 1.5 1.5 % 5.6 5.6 % 2x 26.5 2x40 Ww 2x19 2x27 Ww 2x525 2x525 2 78 114 - V 2 1.9 kQ * + having a voltage adjustment range of +25%. It is essential to provide two seperately adjustable bias voltage sources, Intermodulation distortion; measured using two input signals at 5@ and 6000Hz (ratio of amplitudes 4:1). A It is essential to use two seperate cathode bias resistors.f Chelmer Valve e | electronic tube KT88 q : Va (Vv) | ; 3/3 eee ees